start off by starting to take the rubber cover from the handle, I had this issue previously, water had seeped in and started a swimming pool. I took a flat blad screwdriver and began to prize out the grommit and the swimming pool dispersed, it was problem free after that!

I'd still say check the wiring in the roof conduit to the hatch.
The boot unlocking when braking is is a symptom of a short between the brake light live feed and the boot lock solenoid live feed.
It would point to at least the insulation on the wires being cracked and moisture completing the circuit.

Agree'd, you could have both issues or most likely as Clive said its just the one. To take the rubber out is a 30 second job, so easier to check on the go if you dont have the time immediately to take a look at the wiring, but definitely follow Clive's advice on this one.